In the global marketplace, manufacturers seek to produce high-quality products at low prices. It is thus important to improve yield and process efficiency to minimize production costs. This holds especially true in the technological field of semiconductor fabrication, where manufacturers employ cutting-edge technologies with volume production techniques. One goal of semiconductor manufacturers is to reduce the consumption of raw materials and other consumables while at the same time improving process tool utilization. The latter aspect is of particular importance because, in modern semiconductor facilities, the purchase and operation of the required processing equipment are cost intensive and represent a dominant portion of the total semiconductor production cost.
Integrated circuits and other semiconductor devices are typically manufactured in automated or semi-automated facilities. The manufacturing process is performed, in part, by passing semiconductor substrates through a large number of process steps to complete the fabrication of the integrated circuits thereon. The number and the type of process steps to which a semiconductor substrate is subjected depend on the specifics of the semiconductor device to be fabricated. For instance, a sophisticated central processing unit (CPU) may require several hundred process steps, each of which must be carried out within specified process margins to achieve the required device specifications.
In a semiconductor facility, a plurality of different product types are usually manufactured at the same time, such as memory chips of different design and storage capacity, CPUs of different design and operating speed, and the like. The number of different product types may even reach a hundred or more in some production lines. Each of the different product types may require a specific process flow, and require different mask sets for lithography and specific settings in various process tools, such as deposition tools, etch tools, implantation tools, and chemical mechanical polishing (CMP) tools. Consequently, a plurality of different tool parameter settings and product types may be encountered simultaneously in a manufacturing environment. Further, a mixture of product types, such as test and development products, pilot products, and different versions of products, at different manufacturing stages may be present in the manufacturing environment at any given time. The composition of this mixture may vary over time depending on economic constraints. Still further, it is common that the various product types may have to be processed with a different priority to meet requirements imposed by specific economic, customer, or other constraints.
In order to maximize production efficiency and minimize production costs, it is desirable to coordinate the process flow within the manufacturing environment in such a way that a high degree of tool utilization is achieved. That is, it is desirable for each of the numerous fabrication tools in the fabrication facility to be in use as often as possible, with as little “down-time” as possible. Tool utilization is an important cost factor due to the high investment costs of such tools and the moderately low life span of semiconductor process tools. Tool utilization is thus a significant component in the determination of the price of fabricated semiconductor devices.
Accordingly, it is desirable to provide semiconductor fabrication methods and systems that reduce process tool idle time and increase tool utilization by reducing time intervals between the completion of a processing step on a lot of substrates and the commencement of a processing step on a successive lot of substrates. Furthermore, other desirable features and characteristics of the semiconductor fabrication methods and systems will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings, brief summary, and this background.